Grunt's Loyalty mission in Mass Effect 2 requires he, Shepard, and a third squadmate to fight through waves of enemies on Tuchanka, culminating in an encounter with a Thresher Maw. Thresher Maws are more common in the original Mass Effect than in either of the two sequels, but they are no less terrifying or deadly when Shepard faces the one in the rubble during Grunt's Rite of Passage. A Thresher Maw is a giant, wormlike creature that can spit acid for a devastating AOE attack. While the instructions for the mission only require Shepard's squad to survive the Thresher Maw's attacks for five minutes, killing it can result in greater XP, unique dialogue, and more respect from the krogan.
Like many of the other squadmate Loyalty missions in Mass Effect 2, completing Grunt's Loyalty mission makes it more likely Grunt will survive the endgame Suicide Mission. More than that, however, there are serious consequences in Mass Effect 3 if Shepard does not manage to gain Grunt's Loyalty in Mass Effect 2. Killing the Thresher Maw is not a condition for securing Grunt's Loyalty, but it is worth trying for all the accolades it provides. Here's how to survive against and kill the Thresher Maw during Grunt's Loyalty mission in Mass Effect 2.
How to Kill the Thresher Maw during Grunt: Rite of Passage in Mass Effect 2
Once Shepard presses the Keystone the third time during Grunt: Rite of Passage in Mass Effect 2, the ground will begin to shake, and a voice over the loudspeaker will talk about the krogan's only goal being survival against the genophage. Shepard and their squad will see a blue antenna somewhere in the distance. Shooting at it will get the creature's attention and cause it to surface, starting the five minute clock. It will also eventually surface on its own.
The Thresher Maw's main attack is to spit acid, which causes AOE damage. It will usually attack three times, then tunnel underground and change locations. Shepard can follow where it goes due to the plumes of dust it kicks up as it moves. It is also covered in armor, which Shepard and their squad will need to break through to take the creature down. If it lands a hit against Shepard and damages their shields, it will take shields significantly longer to recover than usual. It only takes about three consecutive direct hits to kill Shepard, so finding cover will be imperative.
Many of the metal pillars on the upper pavilion can be destroyed in one hit by the Thresher Maw's acid spit, but any of the pillars reinforced by concrete, particularly the ones closer to the Thresher Maw, cannot be destroyed. These are the best places to seek cover. Shepard should hug the column and change sides when the Thresher Maw moves to ensure they are fully protected at all times. Players who have built Shepard as an Infiltrator should know they will not be protected while Cloaked, and the Thresher Maw can still accurately target, attack, and kill them.
The most vulnerable point to aim for on the Thresher Maw is its blue tongue. It appears to take more damage when shots land there than anywhere else. Shepard should choose their third squadmate carefully, as detonation and incineration abilities like Inferno Grenade, Incinerate, Incendiary Ammo, Armor-Piercing Ammo, and Reave are effective. Additionally, using Concussive Shot from Grunt when the Thresher Maw surfaces will stagger it, causing it to attack fewer times before its retreat for that round.
While heavy weapons like the Cain and the Collector Particle Beam can be useful to chip away at the Thresher Maw's armor, Heavy Pistols are just as effective if upgraded beforehand. Players can also choose weapons with inherent increased armor penetration abilities if they do not have Armor Piercing Ammo available.
Once Shepard and their team defeats the Thresher Maw in Mass Effect 2, Grunt's Rite will end, even if there is still time left on the clock. For defeating the Thresher Maw, Shepard will receive 937 Experience rather than the usual 750. Other krogan will react to the news and express respect for Shepard and Grunt. Shepard will also learn that no krogan from Clan Urdnot has managed to kill a Thresher Maw during the Rite except Wrex. Finally, upon returning to Tuchanka, EDI will inform Shepard that there have already been breeding requests for Grunt, along with one for Shepard, based on their slaying of the creature.
Mass Effect: Legendary Edition launches May 14 for PC, PlayStation 4, and Xbox One, with forward compatibility on PlayStation 5 and Xbox Series X/S.